For slotting the heads of bolts or studs having hexagonal heads, there are various machines known, including for instance the machine according to U.S. Pat. No. 3,585,665.
Known machines such as that of U.S. Pat. No. 3,585,665 make possible a slotting of the hexagonal heads of such bolts only diametrically, or in a direction corresponding to that of a line interconnecting oppositely located corners of the hexagonal heads. Such known machines do not make possible, as is often required, a slotting which is naturally centered and at right angles to opposite edges of hexagonal heads.